Yellow color shows thiamine degradation on an agar plate of P. thiaminolyticus strain 8120.  Photo credit: Catherine A. Richter, Columbia Environmental Research Center.

Reproductive success of salmonines, including lake trout, in the Great Lakes has been limited by early mortality syndrome (EMS) due to thiamine (vitamin B1) deficiency in eggs.  The Gram-positive bacterium Paenibacillus thiaminolyticus produces an enzyme, thiaminase I, which degrades thiamine.  While thiamine deficiency may have multiple causes, P. thiaminolyticus is one potential cause of thiamine deficiency leading to EMS in Great Lakes salmonines.  Diets of alewife or isolated strains of P. thiaminolyticus mixed in a semipurified diet and fed to lake trout have been shown to produce EMS in fry.  Furthermore, P. thiaminolyticus has been isolated from viscera of alewife collected in Lake Michigan.  In order to aid studies of the sources of P. thiaminolyticus and thiaminase I, we have developed and characterized quantitative PCR assays for the thiaminase I gene and the 16S rRNA gene of P. thiaminolyticus.  These Q-PCR assays are being applied to identify sources of bacterial thiaminase I in Great Lakes food webs and will be of use in defining the relative importance of this cause of thiamine deficiency and in evaluating the effectiveness of management strategies for prevention of EMS in Great Lakes salmonines.

For more information, contact Catherine A. Richter, Columbia Environmental Research Center.

Great Lakes. Photo credit: Jeff Schmaltz/NASA

Viral hemorrhagic septicemia (VHS) is considered to be the most important viral disease of finfish worldwide and is listed as reportable by many nations and international organizations. Prior to 1988, VHS was not known to occur outside of continental Europe where it affected rainbow trout aquaculture. Subsequently, a North American strain of the causative rhabdovirus, VHSV, was found to be endemic among marine fish on the Pacific coast of North America where it was shown to be highly pathogenic for marine species, especially herring. Surveys in other regions of the world have revealed that VHSV is also endemic among marine species in the North Atlantic, the Baltic Sea, the North Sea and Japan. Beginning in 2005, reports from the Great Lakes region indicated that wild fish had experienced disease or, in some cases, very large die-offs from VHS. The USGS Western Fisheries Research Center (WFRC) has conducted research on VHSV for more than 20 years providing technical assistance and information to fisheries managers at state, federal, tribal and private sector entities as well as to the news media. Research at the WFRC has developed novel tools for the detection and identification of VHSV and used molecular epidemiology to show that the strain of VHSV affecting fish in the Great Lakes Basin is a new genotype of the virus, now identified as Genotype IVb. The type IVb isolate found in the Great Lakes region is the only strain of VHSV that has been linked to large natural mortalities among freshwater species. As of spring 2008, VHSV has been isolated from more than 25 species of fish, some of which suffered substantial mortality, in Lake Michigan, Lake Huron, Lake St. Clair, Lake Erie, Lake Ontario and the St. Lawrence River as well as inland lakes in Wisconsin, Michigan and Ohio.

Links to VHSV Fact Sheets:

• Detection of Viral Hemorrhagic Septicemia Virus (PDF; 322 KB)
• Molecular Epidemiology of Viral Hemorrhagic Septicemia Virus in the Great Lakes Region (PDF; 699 KB)

For further information contact James R. Winton, Western Fisheries Research Center.